Mac: With Yosemite, you can create your own voice commands on your Mac using Automator. Blogger Jacob Salmela points out that if you like to live on the edge, you can make a voice-activated self-destruct sequence.
All you need to do is set up an Automator action that runs a command like
rm -rf / that deletes everything on your hard drive. Obviously, most of us don't have any use for this, but if you're worried and want an easy way to clear everything off your hard drive with a voice command, this is the way to do it.